Abstract

We have fabricated assemblies of molecular junctions comprised of superparamagnetic nanoparticlesself-assembled with alkane molecules of different lengths as the spacer. The electrical resistance increases exponentially over nearly two decades as the molecular length varies from 0.7 to 2.5 nm, indicating that electrons tunnel through the molecules that are chemically bonded with nanoparticles. Up to room-temperature magnetoresistance is observed. Remarkably, the tunnelingmagnetoresistance ratio stays nearly independent of molecular length, which entails room-temperature spin-conserving transport in organic molecules.

Received 01 March 2011Accepted 06 April 2011Published online 25 April 2011

Acknowledgments:

We thank W. Y. Zhang and D. Y. Xing for helpful discussion. This work is supported by NSF of China (Grant Nos. 10804046, 10974084, and 11023002) and Jiangsu Province (Grant No. BK2008256), National Basic Research Program of China (Grant Nos. 2007CB925104 and 2010CB923402), NCET project (Grant No. NCET-08-0266), and RFDP of Higher Education (Grant No. 200802841044). S.W. is partially supported by the Scientific Research Foundation of Graduate School of Nanjing University. J.S. acknowledges the support by DOE (Grant No. DE-FG02-07ER46351).